[Lexander]

Ya, I realised that driving home, and then crashed after class. I knew something was wrong but hadn't pinned it down.

That I suppose addresses much of the question. The estimated standard deviation per hand is sounding like 1.5BB-2.00BB per hand. Higher than I would have thought given how often I fold but win rates are highly skewed. Kind of scary to think that a sample size of 10,000 produces a test with such low power.

And since you were picky about me using a 2-sided t-test (my range, btw, was from a 1-sided t-test but I used a conservative 20BB estimate just to impose more restriction), I will be picky about you referring to it as my 1-sided Confidence Interval. T tests might have a nice CI representation but the test itself is against a 5% upper tail critical region.